Balsarite is good stuff, like to other guys said, it needs to be thinned. I used it on the tail of a T-28 about 10 years ago (I've used it a lot more than once). I recently decided to glass the T-28. Man, pulling that fabric off of the wood/balsarite, tough job. It pulled some of the wood off with the fabric! I had to sand & fill the sheeting again.

Mike